Known in the art is a process for preparing an organophosphorus compound employed as a scaling inhibitor comprising reacting polyethylenepolyamines with formaldehyde and phosphorous acid at a temperature of 100.degree.-110.degree. C. in hydrochloric acid (cf. USSR Inventor's Certificate No. 401692, Cl. C 08 G 33/06, 1974).
This prior art process has a disadvantage residing in that the resultant inhibitor has a low protective antiscaling effect. Furthermore, the process features a high synthesis temperature.
Also known in the art is a process for preparing a scaling inhibitor by reacting formaldehyde, phosphorous acid, a mixture of polyethylenepolyamine, monoethanolamine and carbamide, as well as ammonium chloride and/or hexamethylenetetramine in a mass ratio of 100:55-75:25-40:50-70:34-35 at a temperature of 98.degree.-100.degree. C. (cf. USSR Inventor's Certificate No. 719970, Cl. C 02 B 5/00).
A disadvantage of this process resides in that the thus-prepared inhibitor has a low anstiscaling effect. Moreover, the process itself has a high temperature of the synthesis.
Another prior art process for preparing a scaling inhibitor comprises reacting formaldehyde with phosphorous acid and a nitrogen-containing condensation product obtained by interaction of dischloroethane and aqueous ammonia at a temperature of from 110.degree. to 135.degree. C. This condensation product has the following composition, percent by mass:
______________________________________ polyethylenepolyamine hydrochloride 38 to 70 ammonia 0.1 to 1.0 ammonium chloride 1.0 to 6.0 water 25 to 27. ______________________________________
The synthesis of the inhibitor is conducted at a temperature of 98.degree.-100.degree. C. in a medium of diluted hydrochloric acid, followed by alkalization of the resultant solution with sodium hydroxide to a pH of 3.6-3.9 (cf. USSR Inventor's Certificate No.726123, Cl. C 08 G 79/04).
A disadvantage of this process resides in the use of high temperatures for the synthesis. Furthermore, the thus-produced scaling inhibitor is less effective in stabilization of oversaturated solutions of mineral salts.
Still another prior art process for preparing a scaling inhibitor comprises treatment of a mixture containing amines (polyethylenepolyamine, monoethanolamine), ammonium chloride and carbamide with formaldehyde and phosphorus trichloride in an aqueous medium at a temperature of 98.degree.-100.degree. C., followed by distilling-off the resulting phosphorous acid from the reaction mass and neutralization of the latter with an alkali metal hydroxide (for example, sodium hydroxide) to a pH of 3.7-3.8 (cf. USSR Inventor's Certificate No. 791645, Cl. C 02 F 5/12, 1980).
A disadvantage of this process resides in the use of high temperatures for the synthesis. Furthermore, the thus-produced scaling inhibitor is but less effective against scaling, especially barium sulphate scaling.
Known in the art is a process for preparing a scaling inhibitor which comprises reacting formaldehyde, phosphorus trichloride and amines (the process of phosphonomethylation) in an aqueous medium at a temperature of 35.degree. to 50.degree. C. As these amines a product is used which is prepared by reacting epichlorohydrin and ammonia in the form of an aqueous solution at a temperature of 10.degree.-15.degree. C. and a molar ratio of the reagents of 1:5-15 respectively, followed by treatment of the reaction mass with an alkali metal hydroxide in an amount of 1.0-1.1 mol per mol of epichlorohydrin and distilling-off the unreacted ammonia with a subsequent vacuum fractionation to give a product comprising 1,3-diaminopropanol-2 and/or polyhydroxypropylenepolyamines of the general formula: ##STR2## wherein n=2-5. The reaction of amines with formaldehyde and phosphorus trichloride is effected at their molar ratio of 1:4.3-4.6:3.66-4.0 (cf. British Pat. No. 1,479,381 Cl. C 07 F 9/38, C 02 B 5/06).
The inhibitor prepared by this process is less effective against scaling.
A further process known in the art for the preparation of a scaling inhibitor comprises reacting 1,3-diaminopropanol-2 and/or polyhydroxypropylenepolyamines of the general formula: ##STR3## wherein n=2 to 20 with formaldehyde and phosphorus trichloride in an aqueous medium at the temperature of 45.degree. C. and the molar ratio of amines to formaldehyde and phosphorus trichloride of 1:3.79:3.87 respectively (cf. USSR Inventor's Certificate No. 876666, Cl. C 08 G 79/04).
The inhibitor produced by this process has an insufficient protective antiscaling effect.